Deprecate FLAG_quic_use_new_idle_timeout

net/quic/quic_connection.cc

Index: net/quic/quic_connection.cc
diff --git a/net/quic/quic_connection.cc b/net/quic/quic_connection.cc
index d8ab40f485128a3ce639f9d3beaf86d39eb3f127..46636fae13f9e6ec0be2b186b3a860d950578baa 100644
--- a/net/quic/quic_connection.cc
+++ b/net/quic/quic_connection.cc
@@ -2201,14 +2201,8 @@ void QuicConnection::SetNetworkTimeouts(QuicTime::Delta handshake_timeout,
 
 void QuicConnection::CheckForTimeout() {
   QuicTime now = clock_->ApproximateNow();
-  QuicTime time_of_last_packet = QuicTime::Zero();
-  if (!FLAGS_quic_use_new_idle_timeout) {
-    time_of_last_packet =
-        max(time_of_last_received_packet_, time_of_last_sent_new_packet_);
-  } else {
-    time_of_last_packet =
-        max(time_of_last_received_packet_, last_send_for_timeout_);
-  }
+  QuicTime time_of_last_packet =
+      max(time_of_last_received_packet_, last_send_for_timeout_);
 
   // |delta| can be < 0 as |now| is approximate time but |time_of_last_packet|
   // is accurate time. However, this should not change the behavior of